Nocardial infections in the United States, 1972-1974.

A survey of members of the Infectious Diseases Society of America indicated that nocardial infections are not rare. Probably between 500 and 1,000 cases are recognized in the United States each year, of which 85% are serious pulmonary or systemic infections. Although nocardial infections are usually opportunistic infections in the compromised host, at least 15% of the infections in this series occurred in patients without a definable predisposing condition. Nocardial infections occurred in a random geographic distribution within this country, with affected males outnumbering females by 3:1. Most patients were between the ages of 21 and 50 years; however, the age range was broad. The number and variety of infections caused by Nocardia species other than Nocardia species other than Nocardia asteroides have been underestimated. Between 8.6% and 18.8% of pulmonary-systemic infections in this series were caused by species of Nocardia other than N. asteroides.